Asthma is one of the most common chronic illnesses and it disproportionately affects inner-city African Americans. The prevalence rate of asthma has been estimated to be as high as 20 percent among inner-city African Americans which is 2-3 times higher than the national prevalence rate. Moreover, inner-city African Americans experience greater morbidity and have higher asthma-related mortality than others. There are striking differences in environmental exposures between inner-city and suburban homes that may explain the disproportionate asthma burden in the inner-city population. For example, Mus m 1, the major mouse allergen, is found in 95 percent of inner-city homes, and is found in 100-fold higher concentrations in inner-city homes than in suburban homes. In addition, mouse is a well-recognized cause of occupational asthma, and as many as 20 percent of inner-city homes have levels of airborne mouse allergen that are as high as levels seen in some occupational settings. The striking prevalence and high levels of Mus m 1, a known causative agent of occupational asthma, suggest that Mus m 1 may be a significant contributor to inner-city asthma morbidity. For these reasons, we hypothesize that (i) mouse allergen exposure causes asthma morbidity among inner- city asthmatics and (2) mouse allergen elicits an allergen-specific inflammatory response in the airways of inner-city asthmatics with IgE-sensitization to mouse. In order to establish the link between household mouse allergen exposure and asthma morbidity in inner-city, we propose repeatedly assessing household Mus m 1 levels, and asthma-related health care utilization and symptoms in a cohort of inner-city children and young adults with asthma. In addition, we will conduct nasal and bronchial challenges to mouse allergen in order to determine if skin test sensitivity to mouse allergen predicts airways symptoms and allergic inflammatory responses to mouse allergen. The findings from these studies will directly inform public health strategies to reduce the inner-city asthma burden, and lend critical insight into the clinical implications of a positive skin test to mouse in the inner-city population.